Method and apparatus for dyeing cellulosic textile substrates with a leuco-state dye

ABSTRACT

An apparatus for dyeing a cellulosic textile substrate with reduced indigo dye in a leuco-state in an inert atmosphere substantially isolated from oxidizing substances. A plurality of applicator faces that each apply a portion of the total dye application. The first foam applicator is spaced from the entrance of the chamber to allow air entrapped in the interstices of the substrate to escape. The applicators are spaced from each other to allow collapse of the foam and dispersion of the dye applied in the previous applicator before the substrate reaches the next applicator. Similarly, the exit is spaced from the last applicator to allow the foam to collapse and the dye to disperse prior to exiting the apparatus and entering the atmosphere in which oxidization of the dye occurs.

This application is a continuation-in-part of pending U.S. patentapplication Ser. No. 10/833,450, filed Apr. 28, 2004.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for dyeing cellulosictextile substrates with an inert leuco-state dye. More particularly, thepresent invention relates to an apparatus for dyeing cellulosic textilesubstrates with a reduced leuco-state dye foamed with an inert gas andapplied in the leuco foamed state in an inert atmosphere to the textilesubstrate and subsequently oxidized thereon to affix the indigo dye tothe cellulosic textile substrate.

Dyeing cellulosic textile material, such as cotton yarn or fabric, witha leuco-state dye, such as indigo dye, has a large market, particularlyfor cotton denim clothing items, such as blue jeans. The fastness of theindigo dye on cotton and the deep color or shade that can be obtainedmake indigo dyed fabric a very popular product. However, dyeingcellulosic textile material with indigo dye is a complicated, complexand expensive procedure, because indigo in its natural state will notaffix to cellulosic fibers. To render the indigo dye capable of affixingto cellulosic fibers, it is necessary to reduce the indigo by removingoxygen as by mixing with hydro (hydrogen sulfide) or other reducingagents to render the indigo a colorless leuco-state material. It thenmust be handled to remain in a substantially leuco-state until it isapplied to the cellulosic textile material. To be capable of beingapplied, the leuco-state indigo dye must be sufficiently dilute topenetrate into the interstices of the cellulosic material. Typically,indigo dye is obtained from a supplier in a paste form that is, forexample, in a 40% solution. It then must be further diluted to, forexample, a 2% solution with a non-oxidizing liquid, such as hydro, to becapable of penetration into a traveling textile substrate that isimmersed through a vat of the diluted indigo dye. Because of thisdilution, it is necessary to pass the textile substrate through a seriesof sequential indigo dye vats with intermediate exposure to theatmosphere or other oxidizing agents to set the indigo applied duringthe preceding immersion. To obtain a desired deep color or shade, it iscommon to utilize a dyeing range having anywhere from four to eight, dyevats in series with arrangements of guide rolls between vats to assureproper oxidation of the indigo between vats. In addition, the dye in thevats must be continuously and rapidly recirculated in a tank or tanksinto which reduced water or other similar material is added andregulated to remove oxygen taken up in the dye vats and to return anyoxidized indigo dye to the reduced leuco-state.

A significant problem with prior art indigo dyeing ranges is that ofwaste dye and water disposal. Because of the numerous vats and theamount of dye liquor that must be provided, there is a significantquantity of dye liquor that must be disposed of at the end of everydyeing operation. This creates an undesirable substantial expense andenvironmental problem.

Another prior art dyeing system is disclosed in U.S. Pat. No. 4,613,335,issued Sep. 23, 1986, to Hans-Ulrich Berendt, et al. This patentdiscloses a process for dyeing or printing cellulosic-containing textilematerial with a reduced leuco-state dye in a foam carrier. Whilementioning dyeing, the disclosure is primarily directed to printing, andthere is no disclosure of the substrate being in a sealed, inertatmosphere. Rather, the substrate is exposed to the atmosphere as itapproaches the applicator, as it passes across the applicator, and as itleaves the applicator. Therefore, there is no control of the conditionof the substrate as it approaches and passes under the applicator and nocontrol of the oxidation of the dye after it is applied to thesubstrate.

In contrast, the present invention provides for the applicator face andsubstrate to be in a controlled inert atmosphere so that the foam can beapplied without oxidation or controlled oxidation of the leuco-state dyeand the foam can at least partially collapse in the inert atmosphereallowing the dye in its leuco-state to disperse on the substrate withoutoxidation or with controlled limited oxidation before it is fullyoxidized as the substrate leaves the inert atmosphere, assuring thatdesirable affixing of the dye on the substrate occurs when the substrateis exposed to the atmosphere.

SUMMARY OF THE INVENTION

Briefly described, the present invention provides an apparatus fordyeing cellulosic textile substrates with a foamed reduced leuco-statedye. The apparatus includes a housing having an interior chamber sealedfrom atmospheric air and through which the substrate travels from anentrance having a seal through which the substrate enters the chamber toan exit having a seal through which the substrate exits the chamber. Asupply of inert gas communicates with the chamber to provide an inertenvironment therein. At least one foam applicator has an applicator facein said chamber and extending across the width of the substrate forapplying foam containing the dye in leuco-state to the substrate in thechamber. A foam generator generates foam containing the leuco-state dyein the absence of oxygen with the generator communicating with theapplicator for supplying the foamed leuco-state dye to the applicator.Thus, oxidation occurs primarily only after the substrate exits thechamber. However, there may be a minimal amount of oxygen in theotherwise inert gas and some small controlled amount of oxygen maypurposely be included in the inert gas for desired controlled partialoxidization of the dye before it exits the chamber. Preferably, thesupply of inert gas is under pressure to provide a pressurized inertenvironment in the chamber and minimize the entry of any atmospheric airthrough the entrance and exit. Also, preferably, the at least oneapplicator is spaced from the entrance to provide a free reach of thesubstrate in which air trapped in the interstices of the substrate isallowed to escape, and the at least one applicator is spaced from theexit to allow foam on the substrate to collapse and deposit anddistribute the leuco-state dye on the substrate before the substrateexits the chamber and the dye is oxidized.

In a preferred embodiment there is a plurality of applicators withapplication faces in the chamber and disposed with spaces therebetweento allow foam to at least partially collapse and the leuco-state dye toat least partially deposit on the substrate before having foam appliedby the following applicator. Hold-down elements, in the form of rollers,may be disposed between the applicators for engaging the substrate todisplace the substrate between the applicators to maintain the substratein foam receiving engagement with the applicator faces. The applicatorsare preferably parabolically shaped for uniform distribution of foamacross the width of the substrate.

In the preferred embodiment, the inert gas is nitrogen and the foamgenerator generates a foam of nitrogen containing the leuco-state dye.One advantage of nitrogen being in the foam is that when the foamcollapses in the chamber, the nitrogen increases the amount of inertnitrogen in the chamber environment.

The present invention has special application to dyeing woven denimfabric with indigo dye, which may be applied at a weight ofapproximately 10% to 15% of the weight of the fabric.

To allow access into the chamber, the housing may have an openable coversealingly mounted thereon and the hold-down elements may be mounted on aframe that is moveable to move the hold-down elements away from thespaces between applicators when the cover is open.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of a dyeing range in which the apparatus ofthe preferred embodiment of the present invention is incorporated;

FIG. 2 is a plane view of the dyeing range of FIG. 1;

FIG. 3 is an end elevation of the entrance end of the dyeing apparatusincluded in the dyeing range of FIGS. 1 and 2;

FIG. 4 is a plane view of the apparatus of FIG. 3 with a portion of thecover removed;

FIG. 5 is a side elevation of the apparatus of FIG. 3;

FIG. 6 is a side elevation of the apparatus of FIG. 3 with the sidepanel removed;

FIG. 7 is similar to FIG. 6 with the cover and roller frame open; and

FIG. 8 is a view similar to FIG. 6 and illustrating alternative exitseals and drains.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The dyeing apparatus 10 of the preferred embodiment of the presentinvention is illustrated in FIGS. 1 and 2 incorporated in a dyeing range12. A sheet of textile substrate S is fed to the range 12 from a supplyroll 14 or a supply of plaited material in a supply box 16. Thesubstrate S is then relaxed in a J-box 18 from which it is withdrawn bya feed roll assembly 20 from which the substrate travels under acrosswalk grid 48 on which an observer O stands to monitor the dyeingoperation in the dyeing apparatus 10. The substrate is drawn through thedyeing apparatus 10 by a driven pull roll assembly 22. The drive of thefeed roll assembly 20 and pull roll assembly 22 are controlled so that adesired tension is being maintained in the substrate S as it travelsthrough the apparatus 10. From the pull roll assembly 22 the substratemay be subjected to a supplemental treatment at a supplemental dyeapplication station 24, at which a foam applicator 26 applies a surfacetreatment, such as the same or different dye as applied in the dyeingapparatus 10, or any other desired surface treatment material, whichsurface treatment can be applied to either surface of the substrate. Thetreated substrate then passes through an infrared dryer 28 to reduce themoisture content to a desired level. Any other type of dryer could besubstituted. From the dryer 28, the substrate S passes under a crosswalkgrid 50 over a series of guide rolls 30, and is wound on a driven takeuproll 32 to form a roll 34 of the dyed substrate S.

As illustrated schematically in FIG. 2, an inert gas is fed to thedyeing apparatus 10 from a source 36, which can be a supply tankcontaining the inert gas or a generator of the inert gas, such as anitrogen generator. The gas is fed through a supply line 40 to theinterior of the apparatus 10 to provide an inert environment.

The inert gas is also fed, from the source through a second supply line38 to a foam generator 42, which also receives a reduced, leuco-statedye from a dye supply tank 44. The dye supply tank 44 is maintainedunder seal that prevents air from entering the supply tank 44 as dye isfed therefrom to the foam generator 42 so as to prevent oxidation of theleuco-state dye. The foam generator is of any conventional type that cancreate a foam using the nitrogen and having the dye dispersed therein,which foam is then fed through a feed line 46 into the dyeing apparatus10.

The dyeing apparatus 10 is illustrated in detail in FIGS. 3-8. A frontguide roll 52, under which the substrate travels, directs the substrateS from a horizontal direction to a vertical direction. The front guideroll 52 is mounted on the housing 54 of the dyeing apparatus 10.

As the substrate S travels vertically from the front guide roll 52, itsedges E pass through a pair of opposed sensing forks 56, illustrated inFIGS. 3 and 4, that sense the location of the edges E. In response tosensing of the position of the edges E of the substrate S, servo motors58 adjust end seals 60 to limit foam application to the lateral extentof the substrate without significant escape of foam from the applicatorsbeyond the position of the lateral edges E of the substrate S.

The housing 54 is formed with opposite side panels 64 and corner supportlegs 66. The upper portion of the housing 54 is formed as a chamber 68formed by front and rear walls 70, 71, the side panels 64 of thehousing, a bottom wall 72, L-shaped walls 73 extending from the bottomwall 72 to entrance and exit seals 92 and 126, and a pivotable cover 74that sealingly seats on the upper edges of the walls 70 and panels 64with sealing material, such as resiliently compressible foam material,disposed therebetween, or the seal could be provided by a troughcontaining water formed at the top of the walls 70 and panels 64 withthe bottom edges 76 of the cover seated within the water in the trough(not illustrated). The cover 74 is opened and closed by a pair oflaterally spaced piston cylinder mechanisms 78 that have ends 80attached centrally to the cover 74 and other ends 78 attach toupstanding support posts 84 that extend upwardly from the top of thehousing 54. To accommodate this pivoting of the cover 74, it is mountedon a pivot shaft 86, on which are also mounted support bars 88 adjacentthe piston cylinder mechanisms 78 and centrally of the cover 74. Thesesupport bars 88 stabilize the cover 74 during pivoting.

The cover 74 is formed with observation windows 90 through which theobserver O can monitor the operation of the dyeing apparatus 10 as thesubstrate S travels there-through. At the front of the chamber 68 theentrance seal 92 is located through which the substrate S passes intothe chamber 68. This entrance seal 92 is formed by two pairs of spacedinflatable bladders 93 that prevent the entry of air into the inertenvironment within the chamber 68. Above the entrance seal 92 anentrance guide roll 94 directs the substrate S to a plurality oflongitudinally spaced foam applicators 96, 98, 100, 102 and 104. Theguide roll 94 is located below the level of the face 106 of the firstfoam applicator 96 to ensure positive engagement of the substrate S withthe applicator face 106.

The applicators 96, 98, 100, 102 and 104 are mounted on the bottom wall72 by flanges 103 on the applicators secured on the bottom wall 72.

A hold-down roller mounting frame 108 is mounted above the foamapplicators 96. This frame 108 has mounted on its underside fourhold-down rollers 110, 112, 114 and 116. These hold-down rollers 110,112, 114 and 116 are disposed between the foam applicators and projectdownwardly below the level of the faces of the applicators to force thesubstrate S to be deflected downwardly between applicators to assurepositive engagement of the substrate S with the applicator faces 106.

The frame 108 carrying the hold-down rollers 110, 112, 114 and 116 ispivoted on a pivot shaft 178 spaced rearwardly and upwardly from thelast foam applicator 104. The frame is retained in operating position bywingnuts 180 attachable to upstanding brackets 122 forwardly of thefirst foam applicator 96. A coil spring 121 secured to the rear wall 71of the chamber 68 and a rearward extension 140 of the frame 108 biasesthe frame 108 to an open position so that when the wingnuts 120 arereleased, the frame 108 will pivot upwardly into an open position.

Beyond the last foam applicator 104, an exit guide roll 124 is mountedbelow the level of the foam applicators for guiding the substrate S awayfrom the foam applicators and downwardly through the exit seal 126having pairs of spaced inflated sealing bladders, with the exit seal 126and bladders 128 being identical to the entrance seal 92 and bladders93, to prevent entrance of atmospheric air into the chamber 68.

Spaced below the exit seal 126 is a guide roll 130 that guides thesubstrate vertically downward and then horizontally outward to the pullroll assembly 22.

The entrance seal 92 and the entrance guide roll 94 are spaced from thefirst foam applicator 96 to provide a free reach of the travelingsubstrate during which air that may have been entrapped in theinterstices of the substrate S and thereby entered the chamber 68 willhave an opportunity to escape from the substrate interstices, therebysubstantially avoiding any undesirable oxidation of the reduced,leuco-state dye when it is applied to the substrate.

The foam applicators 96, 98, 100, 102 and 104 are spaced from each otherso that, as the substrate travels from one to the next, it is deflectedby the intermediate guide rolls 110, 112, 114 and 116 to provide a freetime between applicators for the foam to collapse and the dye dispersebefore dye is applied by the next applicator. Similarly, the exit guideroll 124 and exit seal 126 are spaced from the last foam applicator 104to allow collapse of the foam and dispersion of the dye before thesubstrate leaves the inert atmosphere within the chamber 68 and the dyeexposed to oxygen in the atmosphere beyond the exit seal 126.

Each of the foam applicators 96, 98, 100, 102 and 104 are, in thepreferred embodiment, parabolically shaped applicators of the typedisclosed in U.S. Pat. No. 4,655,056, issued Apr. 7, 1987, to Dieter F.Zeiffer. This type of applicator is particularly useful in that theparabolic shape distributes foam equally and over equal distances fromthe input to the full extent of the applicator face. Other types ofapplicators can also be used with varying results.

The applicator in the supplemental dye applying station 24 may also beof the parabolic shape, particularly if it is applying a foam, but anyother type of dye or other surface treatment may be applied as well inother types of applicators.

As seen in FIGS. 6 and 7, gutters 131 at each side of the chamber 68outwardly of the applicators decline centrally toward drain pipes 132that collect any excess dye or other liquid and have closures 134 thatare openable at the end of a dye run to allow flushing of the chamber68. The closures 134 also are open at the startup when nitrogen or otherinert gas is fed from the inert gas source 36 under pressure into thechamber 68. As atmospheric air is heavier than nitrogen, theintroduction of nitrogen under pressure will cause atmospheric air toexit the closure 134. When all or substantially all of the atmosphericair has exited the chamber 68, the closures 134 are sealed and thesubstrate S is threaded by a lead sheet or other means to beginoperation. Alternatively, the substrate may be threaded before air isevacuated from the chamber 68, which will result in a short length ofsubstrate being imperfectly dyed.

The purging of oxygen bearing air from the interstices of the fiberstructure provided by the spacing of the entrance seal 92 and entranceguide roll 94 from the first applicator 96 prevents the dye liquor fromoxidizing prematurely and rather allows subsurface liquor migration thatwould be restricted were the dye to oxidize, making it immobileresulting in a loss of control over distribution of the dye molecules.

However, as commercially supplied inert gas, such as nitrogen, containssome small amount of oxygen and as commercial inert gas generators donot produce totally pure inert gas, there may be a minimal amount ofoxygen in the inert atmosphere, resulting in some unintentional slightoxidization of the dye on the substrate before the substrate leaves thechamber. An advantage of the present invention is that, if desired, somesmall controlled amount of oxygen may purposely be included, in anyconventional manner, to provide partial oxidization of the dye on thesubstrate between and/or after dye application before the substrateleaves the chamber and the dye is substantially oxidized in the ambientatmosphere.

If acceptable, only one foam applicator can be incorporated in theapparatus with all of the foam being supplied through that oneapplicator, but preferably a plurality of foam applicators are used witheach applicator applying a fraction, either equally distributed orselectively distributed, depending on preferences, and a much deepershade can be obtained with the same amount of dye by applying multiplefoam applications. With a plurality of foam applicators, with eachapplicator supplying a relatively small limited amount of dye-containingfoam, the migration of the dye into the fiber surface can be acontrolled process. Subsequent relatively small amounts of foam put ontothe same fiber surface area, in a superimposed fashion, will allow for adye enrichment to be achieved. Sequential dye applications areaccomplished without any dye ever being allowed to oxidize until thefinal application is made. The substrate fibers are unable tosatisfactorily absorb large foam volumes that are applied at one, ratherthan a plurality of, applicators.

With the spaces of the dye liquor delivery system filled with reduceddye, the liquor itself, which can be formulated at a low viscosity,incrementally applied to the fiber surface will provide a controlledspecific infusion rate. The lowest viscosity of the foam can bemaintained during the foam application, with the foam being in only atemporary delivery state. The foam collapses almost immediately uponfiber contact and does not hinder the dye infusion process. Thesuper-imposition of incrementally small amounts of liquor with timeintervals, or infusion stages, between each subsequent foam applicationtakes place with the dye being in a non-oxidized state, in strikingcontrast to the prior art.

In the preferred embodiment, indigo dye in its reduced, leuco-state canbe run at normal finishing range speeds, such as about sixty meters perminute. A typical fabric weight would be 400 grams per square meter, anda typical amount of indigo dye to be applied to one side of the fabricmay be, for example, about 10% or 15% of the weight of the fabric, whichcan be divided in any fashion between the five applicators. For example,each applicator could apply 2% of the dye liquor for a 10% total or 3%for a total of 15% total or unequal amounts can be distributed by thedifferent applicators.

FIG. 8 illustrates a modification of the location of the exit seal anddrain pipe. In this arrangement, the exit seal 136 is located in ahorizontal disposition for exit of the substrate horizontally and anexit guide roll 138 similarly located in the manner of the guide rolls110, 112, 114 and 116 mounted similarly on the frame 108, deflects thesubstrate downwardly following the last applicator 104, for guiding tothe exit seal 136.

In this variation the drain pipes 142 are located at the rear of thehousing 54, and the gutters 141 slant downwardly rearwardly to drainliquid from the chamber 146 into the gutters 141 and drain pipes 142 toexit from the drain pipes 142 when the drain pipe closures 148 are open.

Variables, such as liquor flows, substrates speed, chemicalformulations, purity of the nitrogen, degree of fabric preparation andfiber origin can have distinct effects upon the resulting shades. Shadevariations can easily be achieved by varying the number of applicatorsengaged in the liquor application, even though the total flow would bethe same. For example, it is possible to find that the liquor haspenetrated to the back of the fabric substrate at a 15% wet pickup levelthrough one applicator, while there will not be any evidence of liquoron the back of the fabric substrate if the same total wet pickup of 15%is applied in fractionated succession through five applicators.

An interesting advantage to the present invention is that when the foamcollapses, the nitrogen used to create the foam is released into theenvironment within the chamber 68, thereby enhancing the nitrogencontent in the chamber 68 in replenishing any nitrogen that has escapedfrom the chamber. This reduces the amount of nitrogen that must besupplied to the chamber 68.

The number of applicators used in an apparatus according to the presentinvention may be varied from one to as many as six or more, depending onthe application flexibility desired. Further, the application of theliquor can be done at ambient temperature, but, if desired, elevatedtemperatures could be utilized to provide some advantage on certainfabrics and procedures.

When the fabric exits the chamber 68 the reduced, leuco-state dye isalmost instantly oxidized as it is exposed to ambient air.

While the drawings illustrate and the detailed description describes anapparatus having four applicators, it should be understood that theapparatus can be operated with all or less than all applicators,including with only one applicator, actively applying foamed dye, andthat the invention may be practiced with apparatus made with only oneapplicator therein or any desired number of applicators, all of whichmay be active or some of which may be inactive.

The pressure of nitrogen within the chamber 68 need be only slightlymore than atmospheric pressure. It needs to be sufficiently higher thanatmospheric pressure to prevent ambient oxygen-containing atmospherefrom entering the chamber 68 and causing oxidation of the applied dye.

In view of the aforesaid written description of the present invention,it will be readily understood by those skilled in the art that thepresent invention is susceptible of broad utility and application. Manyembodiments and adaptations of the present invention other than thoseherein described, as well as many variations, modifications, andequivalent arrangements, will be apparent from or reasonably suggestedby the present invention and the foregoing description thereof, withoutdeparting from the substance or scope of the present invention.Accordingly, while the present invention has been described herein indetail in relation to the preferred embodiment, it is to be understoodthat this disclosure is only illustrative of an example of the presentinvention and is made merely for purposes of providing a full andenabling disclosure of the invention. The foregoing disclosure is notintended nor is it to be construed to limit the present invention orotherwise exclude any other embodiment, adaptations, variations,modifications and equivalent arrangements, the present invention beinglimited only by the claims appended hereto and the equivalents thereof.

1. An apparatus for dyeing a traveling cellulosic textile substrate witha dye in leuco-state applied in a foam condition, comprising: a housinghaving an interior chamber sealed from atmospheric air and through whichsaid substrate travels from an entrance having a seal through which saidsubstrate enters said chamber to an exit having a seal through whichsaid substrate exists said chamber; a supply of inert gas communicatingwith said chamber to provide an inert environment therein; at least onefoam applicator having an applicator face in said chamber and extendingacross the width of said substrate for applying foam containing said dyein leuco-state to said substrate in said chamber; and a source of foamcontaining said leuco-state dye in the absence of any significant amountof oxygen, said foam generator communicating with said applicator forsupplying said foamed leuco-state dye to said applicator.
 2. Theapparatus of claim 1, characterized further in that said foam contains asmall controlled amount of oxygen.
 3. The apparatus of claim 1,characterized further in that said supply of inert gas is under pressureto provide a pressurized inert environment in said chamber.
 4. Theapparatus of claim 1 characterized further in that said at least oneapplicator is spaced from said entrance to provide a free reach of saidsubstrate in which air trapped in the interstices of said substrate isallowed to escape.
 5. The apparatus of claim 1 characterized further inthat said at least one applicator is spaced from said exit to allow foamon the substrate to collapse and deposit the leuco-state dye on saidsubstrate before the substrate exits said chamber and is exposed to air.6. The apparatus of claim 3 characterized further in that said at leastone applicator is spaced from said exit to allow foam on the substrateto collapse and deposit the leuco-state dye onto said substrate beforethe substrate exits said chamber and is exposed to air.
 7. The apparatusof claim 1 characterized in that said at least one applicator comprisesa plurality of applicators disposed with spaces therebetween to allowfoam to at least partially collapse and said leuco-state dye to at leastpartially deposit on said substrate before having foam applied by thefollowing applicator.
 8. The applicator of claim 7 characterized furtherby hold-down elements between said applicators for engaging saidsubstrate to displace the substrate between applicators to maintain saidsubstrate in foam receiving engagement with said applicator faces. 9.The apparatus of claim 1 characterized further in that said at least oneapplicator is parabolically shaped for uniform distribution of foamacross the width of said substrate.
 10. The apparatus of claim 7characterized further in that said at least one applicator comprises aplurality of said parabolically shaped applicators disposed with spacestherebetween to allow foam to at least partially collapse and saidleuco-state dye to at least partially deposit on said substrate beforehaving foam applied by the following applicator.
 11. The applicator ofclaim 10 characterized further by hold-down elements between saidapplicators for engaging said substrate to displace the substratebetween applicators to maintain said substrate in foam receivingengagement with said applicators.
 12. The apparatus of claim 1characterized further in that said inert gas comprises nitrogen and saidfoam generator generates a foam primarily of nitrogen containing saidleuco-state dye with said nitrogen contributing to the nitrogencontained in said chamber when said foam collapses.
 13. The apparatus ofclaim 1 characterized in that said textile substrate is woven denimfabric and said leuco-state dye is indigo dye applied at a weight aslittle as approximately 10% to 15% of the weight of the fabric.
 14. Theapparatus of claim 1 characterized in that said housing has an openablecover sealingly mounted thereon, said hold-down elements are mounted ona frame movable for movement away from said spaces when said cover isopen.
 15. The apparatus of claim 11 characterized in that said hold-downelements are idler rollers under which said substrate travels.